1. Field of the Invention
The present invention relates to a control method of a gas turbine engine and a control system of the same. More particularly, it pertains to control method and system that are applicable to a control of a gas turbine engine including a multistage combustor.
2. Background Art
In a conventionally known control method of a gas turbine engine, a multistage combustor is formed by dividing the combustor into a pilot combustion chamber (diffusion combustion chamber) and a main combustion chamber (premix combustion chamber). By switching combustions thereof during an operation, an equivalence balance is suitably maintained to restrain a discharge of NOx (nitrogen oxides).
In such a control method of an engine, a sum of the fuel flow rate to be supplied to the pilot combustion chamber and the main combustion chamber is adjusted by means of a fuel adjusting valve located near a source, while a fuel supply is switched from the pilot combustion chamber to the main combustion chamber by means of a switching valve located downstream of the fuel adjusting valve. (See, for example, Japanese Patent Laid-Open Publication No. 206237/1987. See Japanese Patent Laid-Open Publications Nos. 61725/1988, 134825/1987, and 4265/1995 for other control methods of a gas turbine engine including a pilot combustion chamber and a main combustion chamber).
However, there is a disadvantage in such a conventional fuel switching manner. That is, a rotational speed of a turbine may decrease upon switching, because of a delayed filling of a pipe with fuel or an ignition delay, for example. Then, an abrupt ignition of a main burner may destabilize an engine so that a surge, for example, is generated.